EFFECT OF INTRATHECAL OPIOIDS ON SOMATOSENSORY-EVOKED POTENTIALS DURING SPINAL-FUSION IN CHILDREN

Study Design. Intraoperative recording of somatosensory-evoked potenti als is useful for monitoring spinal cord tolerance during spinal fusio n with instrumentation. Volatile anesthetic agents are known to have p rominent suppressive effects on somatosensory-evoked potentials. This study evaluates the effect of intrathecal administration of opioid, co nsisting of morphine sulfate and sufentanil, on somatosensory-evoked p otential monitoring. Objectives. To study the effect of different anes thesia techniques on somatosensory-evoked potentials during spinal fus ion. Summary of Background Data. The effect of intravenous narcotic ad ministration on somatosensory-evoked potentials has been well studied and reported. This study shows the effect of intrathecal opioids on so matosensory-evoked potentials. Methods. Ten patients scheduled for spi nal fusion with Cotrel-Dubousset instrumentation were induced with thi opental and maintained with intrathecal morphine sulfate (20 mu g/kg) and sufentanil 50 mu g, supplemented with isoflurane 0.5% air and oxyg en. Routine monitoring was done, including arterial line and continuou s somatosensory-evoked potentials. Anesthesia was maintained constant, with a mean blood pressure of 55 mm Hg. Normocarbia and normothermia were maintained. Baseline somatosensory-evoked potentials were recorde d using bilateral posterior tibial nerve stimulation, with constant so matosensory-evoked potential monitoring after the induction of anesthe sia. Results. There were no significant changes in either latencies or amplitudes in cortical somatosensory-evoked potentials after opioid i njection at any time during the surgical procedures. Conclusions. Soma tosensory-evoked potential monitoring was possible in all patients und ergoing extensive spinal surgery. Intrathecal opioid anesthesia with l ow concentrations of isoflurane in air and oxygen seems to have no eff ects on somatosensory-evoked potentials.